FITM3 is a 14.6kD (predicted) member of the CD225 family of proteins. It is expressed on primordial germ cells and select tumor types, and appears to regulate cell migration. Human IFITM3 is a 133aa, two-transmembrene protein that contains an N-terminal aa1-57 and a C-terminal aa108-128 extracellular domain. Over aa3-57, human IFITM3 is 59% and 56% aa identical to bovine and mouse IFITM3, respectively. Over aa3-57 human IFITM3 is 88% identical to human IFITM2.